Tunable injecting or extracting optical device for WDM signals as filter to add or drop optical carrier signal or channel - uses thermo-optical effect or electro-optical effect to modify refraction index of one optical path of each phase shift stage

摘要

The tunable optical device comprises a number of directional couplers (AD1-AD6) and a number of phase-shift stages (SF1-SF5), alternately connected in cascade. Each phase shift stage defines a certain optical path length difference (~DL1-~DL5) between two distinct optical paths of the stage, causing a periodic response characteristic with a spectral separation between two adjacent peaks of the periodic response characteristic sufficient to contain all deselected wavelengths of the multiplexed channels when a peak of the periodic response characteristic is centred on a selected wavelength. Tuning is performed by modifying the refraction index of one path of the phase stages by Joule effect heating strips (L1-L5) placed adjacent to a straight portion of one of the two optical paths that compose each phase-shift stage or by metallic field plates adapted to receive a signal suitable to modify the electric field intensity. The first two stages of the phase-shift stages have differences of length of optical paths different from each other and in a preestablished ratio while the remaining phase-shift stages have differences of length of optical paths identical.